Floor Types
Separating floors can be classified into 3 types for the purposes of Part E of the Building Regulations:
Floor type 1 – Resilient material bonded to concrete base with ceiling under. The resistance to airborne sound is largely dependent on the mass per unit area of the concrete base and on the mass per unit area of the ceiling. Impact sound is reduced by the resilient material bonded to the concrete base.
Floor type 2 – Floating layer on concrete base with ceiling under. The resistance to airborne sound is largely dependent on the mass per unit area of the concrete base and on the mass per unit area of the of the floating layer. The floating layer acts to reduce the transmission of impact sound to the concrete base and to the surrounding construction.
Floor type 3 – Floating layer on timber base with ceiling under. The resistance to airborne sound is partly dependent on the mass of the timber base and the absorbent blanket and partly on the mass of the floating layer. The floating layer acts to reduce the transmission of impact sound to the timber base and to the surrounding construction. The mass required for a timber floor is less than that of a concrete floor because the material is softer and radiates sound less efficiently.
Diagram HE28 - Types of floors - Extract from TGD E
Flanking Provisions
To ensure floor construction is fully effective, care should be taken to correctly detail the junctions between the separating floor and other elements such as external walls, separating walls and floor penetrations.
Guidance is provided in the sections following to control flanking transmission at the junction of the separating floor types and other building elements.
Table 5 of Technical Guidance Document E, provided below, details the construction details which should be used at the junction of separating floors and other building elements depending on the floor type being used.
Table HE5 - Reference table of illustrations provided on separating floor junctions - Extract from TGD E
Ceiling Treatments
Reasonable sound insulation is dependent on an appropriate ceiling being provided.
The information below, which is available in section 4 of Technical Guidance Document E, details example ceiling treatments for concrete and timber separating floors. Use of a better performing ceiling than that described in this guidance should improve the sound insulation of the floor provided there is no significant flanking transmission.
It is important to note that the mass per unit area of a sub ceiling should not be included in the calculation of the mass per unit area of the floor.
Example - Ceiling treatment for a concrete separating floor
Plasterboard on timber battens and/ or counter battens. The following specification should be met:
- Create a ceiling void to the underside of the concrete floor using a single layer of plasterboard with a mass per unit area of 10 kg/m2 (min), fixed to timber battens and/or counter battens or proprietary resilient channels/ metal ceiling systems;
NOTE: The sound insulation performance of all ceiling treatments is increased if an absorbent layer of 25 mm (min) mineral wool with a density of 10 kg/m3 (min) that covers the ceiling board area.
Electric cables give off heat when in use and special precautions may be required when they are covered by thermally insulating materials. Refer to BRE BR 262, Thermal Insulation: avoiding risks, section 2.4.
Installing recessed light fittings in ceilings can reduce their resistance to the passage of airborne and impact sound.
Example - Ceiling treatment for a timber separating floor
Plasterboard on timber battens and/ or counter battens. The following specification should be met:
Minimum thickness of 30 mm plasterboard imperforate ceiling in two layers with joints staggered, fixed to timber joists to form fire resisting ceiling;
Provide a sub-ceiling consisting of a single layer of plasterboard with a mass per unit area 10 kg/m2 (min) fixed to the imperforate ceiling using timber battens and/ or counter battens or proprietary resilient channels.
Installing recessed light fittings in ceilings can reduce their resistance to the passage of airborne and impact sound.
Fire resisting ceilings in a timber separating floor should not normally be penetrated without specific fire design complying with Part B – Fire Safety. Therefore, it is recommended that a sub ceiling should be provided below the fire resisting ceiling in order to accommodate services, electric cable runs etc.
Floor Treatments
Each floor type should use an appropriate floor treatment. Detailed below are three specific floor treatments as provided in Technical Guidance Document E. Alternative floating floor constructions may be adopted by following the performance-based approach as detailed in Section 4 of this document.
NOTE: The mass per unit area of a floor treatment should not be included in the calculation of the mass per unit area of the floor.
Where proprietary acoustic products are used, they should be installed strictly in accordance with the manufacturer’s recommendations.
Resilient Material
A resilient material is a material which returns to its original thickness after it has been compressed. Resilient material appropriate for impact sound is a resilient material, or material with a resilient base, with an overall uncompressed thickness of at least 4.5 mm. A material less than 4.5 mm may be suitable where it consists of a resilient covering with a weighted reduction in impact sound pressure level (∆Lw) of not less than 17 dB when measured in accordance with I.S.
ISO 717-2.
NOTE: Products which do not form part of the permanent works and can be readily removed, e.g. carpet, underlay etc are not appropriate for use as resilient layers.
Impact sound reduced at source for FT 1 concrete separating floors
Resilient material bonded to concrete base. A resilient material as described above should be bonded to the concrete floor and will reduce impact sound at source as indicated in Diagram 29 of Technical Guidance Document E which has been provided below for convenience.
Diagram HE29 - Resilient material bonded to concrete base - Extract from TGD E
Floating Floors
A floating floor should isolate the finished floor from the base to reduce impact sound. The following examples are extracts from Section 4 of Technical Guidance Document E
Example - Floating floor suitable for use with a FT 2 concrete separating floor
Timber raft of board material fixed to resilient layer laid on top of the concrete floor as detailed in Diagram 30 of Technical Guidance Document E provided below.
The following specification should be met:
Timber raft of board material (with bonded edges, e.g. tongued and grooved) of thickness 18 mm (min) and mass per unit area of 12 kg/m2 (min) fixed to resilient composite battens of 45 mm (min) deep to meet the performance requirements detailed in Section 3 of this document. The resilient layer must be continuous and pre-bonded to the bottom of the batten, and
Provide 45 mm (min) mineral wool quilt with 10-36 kg/m3 laid between battens.
Example - Floating floors suitable for use with a timber base separating floor
Timber raft of board material fixed to resilient layer, laid on top of a timber base separating floor as detailed in Diagram 31 of Technical Guidance Document E provided below.
The following specification should be met:
Floating layer of 18 mm (min) thick timber or wood-based board with tongue and grooved edges with all joints glued and spot bonded to a substrate of 19 mm (min) plasterboard, or material with at least the same mass secured to:
- Resilient composite battens 70 mm (min) deep complying with performance detailed in Section 3 of this document. The resilient layer of the batten must be continuous and prebonded to the bottom of the batten;
- Provide 60 mm (min) mineral wool quilt with a density of 10-36 kg/m3 laid between battens.
Performance based approach
As detailed in Technical Guidance Document E where a floating floor treatment other than those detailed above is used, it should consist of a rigid boarding above a resilient layer and /or damping layer; with a weighted reduction in impact sound pressure level (∆Lw) of not less than 29dB when measured according to I.S. EN 10140-3 and rated according to I.S. EN ISO 717-2 (refer to Annex B: Supplementary guidance on acoustics measurement standards). The performance value ∆Lw should be achieved when the floating floor is loaded and unloaded as described in I.S. EN ISO 10140 for category II systems.
Diagram HE30 - Timber raft of board material fixed to resilient layer laid on top of the concrete floor - Extract from TGD E
Diagram HE31 - Floating floor treatment suitable for floor type 3 (FT 3) - Extract from TGD E
Floor Type 1
The resistance to airborne sound is largely dependent on the mass per unit area of the concrete base and partly on the mass per unit area of the ceiling. The impact sound at source is reduced by the resilient layer.
The diagrams below, which are provided in Technical Guidance Document E provide the construction details for all the relevant elements to ensure the appropriate level of airborne sound resistance is achieved.
Diagram HE32 - FT 1 Resilient material bonded to concrete base with ceiling under - specification - Extract from TGD E
Diagram HE33 - FT 1 Resilient material bonded to concrete base with ceiling under - flanking requirements - Extract from TGD E
Diagram HE34 - FT 1 Resilient material bonded to concrete base with ceiling under - key junction details (1 of 2) - Extract from TGD E
Diagram HE35 - FT 1 Resilient material bonded to concrete base with ceiling under - key junction details (2 of 2) - Extract from TGD E
Diagram HE36 - FT1 Resilient material bonded to concrete base with ceiling under - services - Extract from TGD E
Floor Type 2
The resistance to airborne and impact sound is largely dependent on the mass per unit area of the concrete base and the mass per unit area and isolation of the floating layer and the ceiling. The transmission of impact sound to the base and the surrounding construction is reduced by the floating layer.
The diagrams below, which are provided in Technical Guidance Document E provide the construction details for all the relevant elements to ensure the appropriate level of airborne sound resistance is achieved.
Diagram HE37 - FT 2 Floating layer on concrete base with ceiling under - specification - Extract from TGD E
Diagram HE38 - FT 1 Floating layer on concrete base with ceiling under - flanking requirements - Extract from TGD E
Diagram HE39 - FT 2 Floating layer on concrete base with ceiling under - key junction details (1 of 2) - Extract from TGD E
Diagram HE40 - FT 2 Floating layer on concrete base with ceiling under - key junction details (2 of 2) - Extract from TGD E
Diagram HE41 - FT 2 Floating layer on concrete base with ceiling under - services - Extract from TGD E
Floor Type 3
The resistance to airborne and impact sound is largely dependent on the mass per unit area of the concrete base and the mass per unit area and isolation of the floating layer and the ceiling. The transmission of impact sound to the base and the surrounding construction is reduced by the floating layer.
The diagrams below, which are provided in Technical Guidance Document E provide the construction details for all the relevant elements to ensure the appropriate level of airborne sound resistance is achieved.
Diagram HE42 - FT 3 Floating layer on timber base with ceiling under - specification - Extract from TGD E
Diagram HE43 - FT 3 Floating layer on timber base with ceiling under - flanking requirements - Extract from TGD E
Diagram HE44 - FT 3 Floating layer on timber base with ceiling under - key junction details - Extract from TGD E
Diagram HE45 - FT 3 Floating layer on timber base with ceiling under - services - Extract from TGD E
